The present invention pertains to a process for the adaptive beam power control of medium-energy laser weapons for fighting electro-optical sensors and windows, wherein a medium-energy laser, a control device with a heat image apparatus, a computer and a laser power controller are associated with the medium-energy laser weapon.
Medium-energy laser weapons are used against electro-optical sensors and against windows, e.g., of combat helicopters. Such a weapon has become known, e.g., under the name MELAS and is described, e.g., in the article xe2x80x9cMedium-energy laser weapon MELAS against helicopter and airplane cockpits and electro-optical sensors, G. Sepp, R. Protz, 2nd German-French Colloquium on Fighting Helicopters, ISL, Saint-Louis, F, Sep. 19-20, 1995, Conference Proceedings. When using such weapons, a surface of small diameter in the case of electro-optical sensors and a surface of large diameter in the case of windows must usually be irradiated with a sufficiently high intensity and for a sufficiently long period of time in order to make the sensor unable to function or to make the window non-transparent. However, the laser power to be emitted for this purposexe2x80x94and subsequently the irradiation time, which it also determinesxe2x80x94can be determined accurately only if the known effect of the thermal beam expansion of a medium-energy laser (xe2x80x9cthermal bloomingxe2x80x9d), i.e., the thermal expansion caused by the absorption-related heating of the propagation channel, is sufficiently taken into account quantitatively. The theory of xe2x80x9cthermal bloomingxe2x80x9d was described, e.g., in the article xe2x80x9cF. G. Gebhard, High power laser propagation, Appl. Opt., 15, 1479 (1976). For lack of a suitable method for including this problem in the fighting procedure, the laser weapons have hitherto been equipped with a control device for the beam intensity, which only sets a maximum laser beam power at all times or at least such a high laser beam power that it is certainly sufficient for the desired fighting effect at the given distance from the target. However, if the laser is usually operated with the maximum power or, for safety reasons, with a power that is actually much too high, more primary energy (e.g., chemical fuel burned in the laser combustion chamber in the case of a gas-dynamic laser) is consumed than would be actually necessary for the desired fighting effect.
There is yet another drawback in addition to this drawback of the prior-art control devices. When the weapon is used against (small-surface) sensors, this method may even lead to an undesired reduction in the fighting effect, because, due to the above-mentioned xe2x80x9cthermal blooming,xe2x80x9d the laser intensity reaching the sensor is lower at the emitted laser power that is actually too high than it would be at a lower emitted laser power.
The primary object of the present invention is to provide a process of the type described in the introduction, in which no such xe2x80x9csafety marginxe2x80x9d is necessary for the emitted laser power any more, so that the lowest possible primary energy consumption is necessary for the desired effect of the laser weapon at the target. In addition, it shall be possible to set the emitted laser power that leads to the maximum attainable laser intensity in the center of the beam at the target. Finally, it shall also be possible to set such an emitted laser power that, taking the expansion ofthe beam of the medium-energy laser due to xe2x80x9cthermal bloomingxe2x80x9d into account, the desired laser beam diameter suitable for fighting the selected target will be obtained at the target.
According to the invention, a process for the adaptive beam control of medium-energy laser weapons is provided for fighting electro-optical sensors and windows. A medium-energy laser, a control device with a heat image apparatus, a computer and a laser power controller are associated with the medium-energy laser weapon. To set the desired laser beam diameter at the target during a measuring phase, the said laser beam of the said medium-energy laser is directed toward the target with an initially lower emitted laser beam power. Subsequently, the computer of the control device progressively increases the beam power up to the maximum possible beam power (Lmax) by means of the laser power controller. The laser power (LG(t)) that is reflected by the bright spot of the target and measured by the heat image apparatus is recorded by the computer. The computer determines the maximum (LG,max) of the laser power from this. During a phase of calculation, the computer calculates the critical laser power (Lc), the critical laser intensity (IC), the laser beam diameter (D (t)) at the target, and the maximum (LG,max(tc)) of the reflected laser power (Lg(t)) measured by the heat image apparatus (13), using the influential parameters which determine the thermal beam expansion and which have been fed into the computer. During a phase of fighting, the computer sets the emitted laser power (L) such that the desired laser beam diameter (D) will be obtained at the target by means of the laser power controller, using the results obtained during the phase of calculation.
The computer may set the critical laser power (Lc) on said medium-energy laser during the phase of fighting.